1. Field of the Invention
The present invention relates to a method and device for controlling motor in a powered seat for an automobile in order to adjust and actuate the movable parts of seating posture adjustment devices according to the physique and taste of an occupant on the seat.
2. Description of Prior Art
In general, a powered seat for automobile is equipped with various seating posture adjustment devices workable under motor controls, such as a seat slide device, a vertical position adjustment device (a seat lifter), and a reclining device.
The motors used in this particular seat are DC geared motor in most cases, and they are connected with motor control devices, permitting their controls to be made by on/off switching operations with associated motor control relays. As a means for stopping the motors is normally formed by a dynamic braking system utilizing a short circuit formation between both terminals of each motor so as to instantaneously cease the drive of motor and keep the motor in such stopped state. The dynamic braking is indeed effective in improving a precision in stopping the motor or the associated movable parts of seating adjustment devices.
In this powered seat, in particular, with regard to such device having a relatively wide movable range as the seat slide device, it is so designed that the associated motors will be driven more rapidly with an increased rotational speed in order to insure more quick movement of the related movable parts of slide device.
However, in the present system, the motor starts to work or stop, quite abruptly, due to the on/off switching operations which causes an abrupt supply or cut of a voltage to the motor. Thus, such abrupt starting or stop operation is transmitted through the devices to an occupant on the seat as a great shock or impact, so that he or she feels uneasy in adjusting or controlling the slide device or other similar device.
Generally, an incentive in solving this problem arises to use a transistor-based motor speed control device having transistors or field effect transistors (FET).
But, such motor control device tends to be complicated in structure and higher in costs, because of those expensive transistors. Further, the transistors are prone to emitting a heat or switching noises, which will adversely affect the adjacent electronic elements and circuits.